iphone 4s don't reset, don't connect to itunes

Hello, I'm ahmtun from Tunisia.

My mother bought an iphone 4GS for me from saudi arabia. In the back of the packet, it mentioned "iphone 4s, black, 64GB", but when I opened it, I have found a white 4gs iphone. That was the first surprise. After that, I have tried to connect it on iTunes, but the diagnostic say that there is no iphone connected and that the apple mobile device driver is not found. As I'm using windows xp SP3, I looked on microsoft website. They say that this problem is an apple problem because the driver belong to apple. Of course I tried some solution given by apple website (reinstall iTunes, ....) but the problem persist. So I decided to reset my iphone, then I was invited to enter a password. I didn't set any password to my iphone. So, I think that someone else tried my iphone in saudi arabia and set a password that I don't know. I want to mention that I have registred my iphone on the apple web site succefully.

Know, I want to restart my iphone to manufacturer settings. I don't know if it's possible in this case and I don't know what's the solution.

Please, I need your help. I'm tired and I start to feel crazy.

Thanks.